1. Field of the Invention
The present invention relates to an adhesive agent in which epoxy compound is mixed with an activator, an inkjet head in which members are adhered to one another by the adhesive agent, and the manufacturing method thereof.
2. Description of Related Art
“Screen printing technique”, which forms a desired pattern on a mesh screen to print ink running through the pattern onto a recording medium, has been widely used for the manufacturing of a liquid crystal color filter, the coating of a liquid crystal orientation film, and the fabrication of various precision electronic components such as organic electroluminescence devices.
However, the screen printing technique is inconvenient because an image cannot be printed easily with low cost. This is due to the fact that a screen must be designed and formed before printing is performed, or a new screen must be designed and formed in every time the pattern is changed. To solve this, the inkjet technique begins to be applied as a substitute technique for the screen printing technique by which an image or the like can be printed easily with low cost.
The inkjet technique is a technique by which an inkjet head for discharging droplets of ink is scanned above a recording medium to record an image or the like on the recording medium. When this inkjet technique is used as a substitute technique for the screen printing technique, since the screen printing techniques are mainly used on a resin-made recording medium as a recording medium (when a resin-made recording medium is used as a recording medium), “solvent-based ink” that easily penetrates through the resin is used to improve durability of the recording medium.
Here, the above inkjet head is structured such that members constituting the inkjet head are adhered to one another by adhesive agent. When solvent-based ink is used, the solvent-based ink may dissolve the adhesive agent. Thus, the adhesive agent is preferably epoxy-based adhesive agent cross-linked under high temperature. A technique applying this has been disclosed in JP 2003-266708A. Specifically, the technique described in JP 2003-266708A uses gradually increasing temperature for drying and curing of adhesive agent from a room temperature to 100° C., so that the crosslinking density is increased to enhance the resistance against the solvent-based ink (see paragraph Nos. 0034 to 0041).
An inkjet head is basically structured such that members constituting the head have different linear thermal expansion coefficients (thermal expansion coefficients) to one another. Thus, when adhesive agent is cured under high temperature, stress exerts between the cured adhesive agent and the members due to shrinkage difference between the members, because the members have different shrinkage factors when the temperature of the adhesive agent returns to a room temperature after the curing. This has a possibility that the members have cracks, distortions, or one member peels from another member.
According to some of the methods for suppressing the above stress, adhesive agent is cured in a low temperature close to the temperature of an environment in which the inkjet head is used (preferably room temperature) or the adhesive agent itself is provided with flexibility. However, adhesive agent which can be cured in a low temperature and which has flexibility has not sufficient resistance against solvent-based ink. Thus, no adhesive agent currently exists that can match the above conditions.
It is an objective of the present invention to provide adhesive agent which can be cured in a low temperature, which has flexibility, and which is resistant against solvent-based ink. It is another objective of the present invention to provide an inkjet head by which members of the inkjet head can be prevented from having cracks, distortions, peeling and the like, and the manufacturing method thereof.
According to a first aspect of the invention, an adhesive agent comprises a base and an activator, wherein the base comprises at least any one of: a first epoxy compound of bisphenol F epoxy compound; a second epoxy compound in which bisphenol F epoxy compound is mixed with an epoxy compound having three or more epoxy groups; and a third epoxy compound in which bisphenol A epoxy compound is mixed with an epoxy compound having three or more epoxy groups, wherein the activator comprises: polyamide composed of a condensation reaction product of C36 unsaturated fatty acid dimer and polyamine, and alicyclic polyamine, the activator containing 5 to 200 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide, and wherein the base is mixed with the activator with a ratio of 10 to 200 parts by mass of the activator with respect to 100 parts by mass of the base.
Preferably, the activator contains 10 to 150 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide, and more preferably, the activator contains 20 to 100 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide.
Preferably, the adhesive agent of the first aspect further comprises fine particles having mean particle size of 0.1 μm or less.
The first aspect can provide adhesive agent which can be cured in a low temperature, which has flexibility, and which is resistant to solvent-based ink (see the following embodiments 1 to 4).
According to a second aspect of the invention, an inkjet head comprises: a channel substrate having a channel of ink, an adherend member adhered to the channel substrate, and a second adherend member further adhered to the adherend member, wherein the channel substrate is adhered with the adherend member, or the adherend member is adhered with the second adherend member by an adhesive agent comprising a base and an activator, wherein the base comprises at least any one of: a first epoxy compound of bisphenol F epoxy compound; a second epoxy compound in which bisphenol F epoxy compound is mixed with an epoxy compound having three or more epoxy groups; and a third epoxy compound in which bisphenol A epoxy compound is mixed with an epoxy compound having three or more epoxy groups, wherein the activator comprises: polyamide containing a condensation reaction product of C36 unsaturated fatty acid dimer and polyamine, and alicyclic polyamine, the activator containing 5 to 200 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide, and wherein the base is mixed with the activator with a ratio of 10 to 200 parts by mass of the activator with respect to 100 parts by mass of the base.
Preferably, the activator contains 10 to 150 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide, and more preferably, the activator contains 20 to 100 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide.
Preferably, the adhesive agent of the second aspect further comprises fine particles having mean particle size of 0.1 μm or less.
Preferably, at least one of differences in linear thermal expansion coefficient between the channel substrate and the adherend member and between the adherend member and the second adherend member is greater than 12 ppm/K.
Preferably, the ink contains 3 mass % or more of solvent having 9.5 to 15.0 of a SP value and 2.0 to 5.0 of a dipole moment to whole solvent weight.
The second aspect uses the above adhesive agent to adhere a channel substrate with an adherend member or to adhere the adherend member with a second adherend member. Thus, stress exerting between the cured adhesive agent and a channel substrate, the adherend member, or the second adherend member can be reduced. Consequently, this can prevent the channel substrate, the adherend member, or the second adherend member from having cracks or distortions, or can prevent the adherend member from peeling off the channel substrate, or can prevent the second adherend member from peeling off the adherend member.
According to a third aspect of the invention, a manufacturing method of an inkjet head, the inkjet head comprising a channel substrate with a channel of ink, an adherend member adhered to the channel substrate, and a second adherend member further adhered to the adherend member, comprises the steps of: applying an adhesive agent comprising a base and an activator at least one of between the channel substrate and the adherend member, and between the adherend member and the second adherend member; and curing the adhesive agent by applying heat of 60° C. or less to the adhesive agent, so that the channel substrate is adhered with the adherend member, or the adherend member is adhered with the second adherend member, wherein the base comprises at least any one of: a first epoxy compound of bisphenol F epoxy compound; a second epoxy compound in which bisphenol F epoxy compound is mixed with an epoxy compound having three or more epoxy groups; and a third epoxy compound in which bisphenol A epoxy compound is mixed with an epoxy compound having three or more epoxy groups, wherein the activator comprises: polyamide containing a condensation reaction product of C36 unsaturated fatty acid dimer and polyamine, and alicyclic polyamine, the activator containing 5 to 200 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide, and wherein the base is mixed with the activator with a ratio of 10 to 200 parts by mass of the activator with respect to 100 parts by mass of the base.
Preferably the base comprises the second epoxy compound.
Preferably, the activator contains 10 to 150 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide, and more preferably, the activator contains 20 to 100 parts by mass of the alicyclic polyamine with respect to 100 parts by mass of the polyamide.
Preferably, the adhesive agent further comprises fine particles having mean particle size of 0.1 μm or less.
Preferably, the adhesive agent is cured by applying heat of 40° C. or less to the adhesive agent.
The third aspect cures the above adhesive agent by applying heat of 60° C. or less to the adhesive agent. Since the adhesive agent has a small temperature difference when the temperature of the cured adhesive agent decreases from the curing temperature to a room temperature, the stress exerting between the adhesive agent and the channel substrate, the adherend member, or the second adherend member is alleviated. As a result, the channel substrate, the adherend member or the second adherend member can be prevented from having cracks, the channel substrate, the adherend member, or the second adherend member can be prevented from having distortions, the adherend member can be prevented from peeing off the channel substrate, or the second adherend member can be prevented from peeling off the adherend member.